Comfort food at its best. The crust ingredients are adapted from America's Test Kitchen.
Cuisine: American, English, French
For the Crust:
2 1/2cupsall-purpose flour
12tablespoonscold, diced unsalted butter
For the White Sauce:
1/3cupbutter (salted or unsalted)
Grinds of black pepper to taste
1teaspoongarlic powder, or to taste
1teaspoondried tarragon leaves, or to taste
2 1/2cupshot milk (or, use a combination of milk and chicken stock)
For the Chicken and Vegetables:
10ouncebag frozen peas and carrots
1/2 to 1 cup diced onion (frozen works well)
2cupscut-up cooked chicken
For glazing the crust:
Making the pastry dough:
Put the flour and salt in the bowl of a food processor. Process briefly just to combine. Add the butter, and pulse approximately 5 times to break up the butter. Stir the egg and sour cream together in a small cup, then add to the flour mixture. Process until the dough just begins to mass on the blade (don't overmix) -- 15-20 seconds. Form the dough into a ball, and then flatten it into a disk. Wrap the disk in cling film and refrigerate for at least one hour (or freeze for up to 2 months).
Rolling out the pastry dough:
Let the dough sit out for approximately 10 minutes. Then cut the dough in half. On a lightly-floured surface or pastry cloth, roll each half into a 12-inch-diameter circle. Transfer one circle to a 9-inch pie pan; place the remaining circle on a parchment-lined baking sheet. Put the pie pan and baking sheet in the refrigerator while you make the white sauce and filling.
The white sauce and chicken filling:
Adjust the oven rack to the lowest position; preheat the oven to 450°F. Meanwhile, melt the 1/3 cup butter in a sauce pan over medium heat. Add the 1/3 cup flour. Whisk the flour and butter together until the mixture bubbles and darkens slightly -- about 1 minute. Add the hot milk, and whisk constantly until the sauce boils and thickens -- about 1 minute.
Off heat, whisk in the salt, pepper, garlic powder, and tarragon. Use a spatula to fold in the frozen peas and carrots, the onion, and finally, the chicken. Taste carefully for seasonings -- you might like to add more salt and/or pepper.
Assembling the pie:
Pour the chicken mixture into the pastry-lined pie pan. Place the remaining crust over the filling. Roll edges under, and flute to seal. Cut 4 slits in the top crust to allow steam to escape.
Brush the crust with the beaten egg.
Baking, cooling, and serving the pie:
Bake on the lowest rack in the preheated 450°F oven until the crust begins to color -- 18-20 minutes. Then lower the heat to 375°F and continue baking until the crust turns golden-brown -- 12-15 minutes. Allow the pie to cool until the filling sets up -- 45 minutes to 1 hour. Serve warm or at room temperature.